Content introduction modal verbs can 11 may 18

E.g. “I’ve seen to it,” he said, but everyone knew it was not true.
Commands and requests, which are problematic actions, are expressed by the Imperative Mood.

The Imperative Mood is the plain stem of the verb (e.g. Come over here. Listen to him, etc.). It may be used in the affirmative and in the negative form The negative form is an analytical form built up by means of the plain stem of the auxiliary verb to do followed by not (don’t) and the infinitive of the notional verb without to (e.g. Don’t go over there. Don’t listen to him, etc.). The negative form of the verb to be is also built up by means of the auxiliary verb to do (e.g. Don’t be inquisitive. Don’t be a fool, etc.).

If we wish to make a command or request more expressive, we use the emphatic form. It’s also an analytical form built up with the help of the plain stem of the auxiliary verb to do which is placed before the notional verb, including to be (e.g. Do come over here. Do listen to him. Do be quiet, etc.).

A command or request is generally addressed to the second person singular or plural. There is usually no need to mention the subject of the action before the verb in the Imperative mood. But occasionally the verb may be preceded by you in familiar style (e.g. You don’t worry.).

A command or request may be addressed to the first person plural. It is also formed with the help of the plain stem of the verb, to let followed by the pronoun us (the contracted form is let’s) and the infinitive of the notional verb. This form is actually an invitation to a joint action (e.g. Let’s have a cup of tea. Let’s do it together, etc.).
Actions represented as unreal are in present-day English express by a variety of forms.

Among them there is a mood form – the conditional Mood.

The fact that there are a number of forms engaged in expressing unreal actions could be explained historically.

In the older periods English used to be a synthetic language and had special forms that served to express unreal actions – the so-called Subjunctive mood. It was built up synthetically by means of inflections. As a result of loss of inflections, the difference between the forms of the Indicative Mood and the Subjunctive Mood has in most cases disappeared. The place of the old Subjunctive Mood was in a number of cases taken up by analytical forms and modal phrases, i.e. combinations of modal verbs with the infinitive. It is this historical process that accounts for the great variety of different forms expressing unreality in modern English.

As some of the forms expressing problematic or unreal actions are modal phrases, it is necessary before describing the different forms of unreality to treat modal verbs first.
The speaker’s attitude towards the action if the sentence may be expressed in different ways:

1. 
   By one of the mood forms that serve to show whether the action is represented as a real fact of as problematic, or unreal, this form of expression is found in every sentence because it is indispensable to predication.
   
2. 
   By modal verbs which represent an action as necessary or unnecessary, possible or impossible, certain of doubtful and the like. But modal verbs need not be used in every sentence and are, therefore, to be regarded as an additional means of expressing the speaker’s attitude towards the action in the sentence.
   
3. 
   By attitudinal adverbs such as certainly, perhaps, probably, luckily, unfortunately, etc. They express different degrees of certainty on the part of the speaker of the desirability of the action from his point of view.